The Lotus Grand Tourers

Hi I've got another problem with the Excel. The reverse lights are staying on all the time. I have pulled the fuse out for the short term. I'm thinking the switch might be stuck or maybe just dirty. Has anyone replaced reverse switch? What I want to hear is the gearbox does not have to come out? Any ideas?

Switch is accessible from the underside of the car, tunnel not too far from the gear stick.

I have an indicator that works, then it doesn't, then it does, then it doesn't, then it does, then it doesn't, then it does...........................